After 10 enjoyable years, I am departing, after an incessant clamor from the left that to permit me continued access to the microphones of MSNBC would be an outrage against decency, and dangerous.

The calls for my firing began almost immediately with the Oct. 18 publication of “Suicide of a Superpower: Will America Survive to 2025?”

A group called Color of Change, whose mission statement says that it “exists to strengthen Black America’s political voice,” claimed that my book espouses a “white supremacist ideology.” Color of Change took particular umbrage at the title of Chapter 4, “The End of White America.”

Media Matters parroted the party line: He has blasphemed!

A Human Rights Campaign that bills itself as America’s leading voice for lesbians, bisexuals, gays and transgendered people said that Buchanan’s “extremist ideas are incredibly harmful to millions of LBGT people around the world.”

Their rage was triggered by a remark to NPR’s Diane Rehm — that I believe homosexual acts to be “unnatural and immoral.”

On Nov. 2, Abe Foxman of the Anti-Defamation League, who has sought to have me censored for 22 years, piled on.

“Buchanan has shown himself, time and again, to be a racist and an anti-Semite,” said Foxman. Buchanan “bemoans the destruction of white Christian America” and says America’s shrinking Jewish population is due to the “collective decision of Jews themselves.”

Well, yes, I do bemoan what Newsweek’s 2009 cover called “The Decline and Fall of Christian America” and editor Jon Meacham described as “The End of Christian America.” After all, I am a Christian.

And what else explains the shrinkage of the U.S. Jewish population by 6 percent in the 1990s and its projected decline by another 50 percent by 2050, if not the “collective decision of Jews themselves”?

Let error be tolerated, said Thomas Jefferson, “so long as reason is left free to combat it.” What Foxman and ADL are about in demanding that my voice be silenced is, in the Jeffersonian sense, intrinsically un-American.

Consider what it is these people are saying.

They are saying that a respected publisher, St. Martin’s, colluded with me to produce a racist, homophobic, anti-Semitic book, and CNN, Fox News, C-SPAN, Fox Business News and the 150 radio shows on which I appeared failed to detect its evil and helped to promote a moral atrocity.

If my book is racist and anti-Semitic, how did Sean Hannity, Erin Burnett, Judge Andrew Napolitano, Megyn Kelly, Lou Dobbs and Ralph Nader miss that? How did Charles Payne, African-American host on Fox radio, who has interviewed me three times, fail to detect its racism?

How did Michael Medved miss its anti-Semitism?

In a 2009 cover story in the Atlantic, “The End of White America?” from which my chapter title was taken, professor Hua Hsu revels in the passing of America’s white majority. At Portland State, President Clinton got a huge ovation when he told students that white Americans will be a minority in 2050.

Is this writer alone forbidden to broach the subject?

That homosexual acts are unnatural and immoral has been doctrine in the Catholic Church for 2,000 years.

Is it now hate speech to restate traditional Catholic beliefs?

Documented in the 488 pages and 1,500 footnotes of “Suicide of a Superpower” is my thesis that America is Balkanizing, breaking down along the lines of religion, race, ethnicity, culture and ideology, and that Western peoples are facing demographic death by century’s end.

Are such subjects taboo? Are they unfit for national debate?

So it would seem. MSNBC President Phil Griffin told reporters, “I don’t think the ideas that (Buchanan) put forth (in his book) are appropriate for the national dialogue, much less on MSNBC.”

In the 10 years I have been at MSNBC, the network has taken heat for what I have written, and faithfully honored our contract.

Yet my four-months’ absence from MSNBC and now my departure represent an undeniable victory for the blacklisters.

The modus operandi of these thought police at Color of Change and ADL is to brand as racists and anti-Semites any writer who dares to venture outside the narrow corral in which they seek to confine debate.

All the while prattling about their love of dissent and devotion to the First Amendment, they seek systematically to silence and censor dissent.

Without a hearing, they smear and stigmatize as racist, homophobic or anti-Semitic any who contradict what George Orwell once called their “smelly little orthodoxies.” They then demand that the heretic recant, grovel, apologize, and pledge to go forth and sin no more.

Defy them, and they will go after the network where you work, the newspapers that carry your column, the conventions that invite you to speak. If all else fails, they go after the advertisers.

I know these blacklisters. They operate behind closed doors, with phone calls, mailed threats and off-the-record meetings. They work in the dark because, as Al Smith said, nothing un-American can live in the sunlight.